Airplane propeller



Aug. 30, 1 938. M. LEFF' AIRPLANE PROPELLER Filed Dec. 20, 1957 Patented Aug. 30, 1938 mam PATENT @FFECE AIRPLANE Michael Left, Buffalo, half to Lawrence C.

PROPELLER N. Y., assignor of one- Lake, Kenmore, N. Y.

Application December 20, 1937, Serial No. 180,739

3 Claims.

This invention relates generally to propellers but more particularly to. a propeller designed for use on airplanes and other aircraft.

It has for one of its objects to provide a propeller of this character which is so designed and constructed as to create a maximum pulling and lifting power with a minimum of slippage.

Another object of the invention is to provide an airplane propeller whose blades are so disposed and shaped as to effectually cut into and grip the air to develop greater power efficiency and propulsive and lifting effort.

A still further object of the invention is to provide a dual bladed construction wherein a plurality of pairs of blades are disposed substantially radially about the axis of rotation in predetermined spaced relation and of such shape as to afford efiicient operation.

In the accompanying drawing:

7 Figure 1 is a perspective view of the propeller embodying my invention. Figure 2 is a side or edge view thereof. Figure 3 is an end View of the same. Figures 4 and 5 are cross-sections taken substantially in the plane of the corre- 25 spondingly numbered lines in Figure 1.

Similar characters of reference indicate corresponding parts throughout the several views.

, Referring now to the drawing, ll) indicates the hub of the propeller which is adapted for attachment in the usual way to the motor shaft of the airplane or other aircraft. Radiating from this hub are a, plurality of pairs of propeller blades ll, l2, there beingv two of such pairs shown in the drawing disposed at the diametri- 35 cally opposite sides of the hub. The blades H,

[2 of each pair are disposed side by side axially of the hub ill .in substantially parallel spaced relation to provide a comparatively narrow air space l3 between the companion blades. The

40 diametrically-opposed pairs of blades are set at a substantially acute angle to their plane of rotation, with the pair of blades at one side of the hub-axis pitched or partially spiralled in one direction and with the pair of blades at the op- 45 posite side of such axis similarly pitched in the reverse direction. By this general dual blade arrangement, as the propeller revolves the blades effectually cut into and grip the air to develop a maximum lifting and propulsive power.

are of such shape and contour as to effectually cut through the air and at the same time guide and direct the air in such a way as to not only exert a greater pulling and lifting power but reduce to a minimum any tendency of the plane The blades of each pair are symmetrical and to skid or side slip. Tothis end, and by preference, the blades it and 12 of a pair are substantially the same shape in elevation or plan contour, and as seen in Figures 1 and 3, the leading edge of the front blade H is disposed slightly forwardly relatively to the corresponding edge of the rear blade l2 and the leading marginal portion of the former is slightly preferably shaped at its front side in the manner indicated at M, while its rear side is convexly curved as indicated at l5 whereby this blade effectually cuts into the air and directs it against the opposing wall of the rear blade and into the space between such blades. The trailing marginal portion of the front side of the front blade H is likewise preferably shaped as indicated at E6, and its trailing edge terminates forwardly of the corresponding edge of the companion rear blade. This rear blade ll of each pair is preferably dished or concave on its rear side and the contiguous marginal portion thereof is convex, as indicated at ii to provide a leading edge for such blade which will effectually cut into the air. The trailing marginal portion of the front side of the rear blade i2 is convexly curved, as indicated at it, and by thus shaping the blade, as

the propeller revolves in counter-clockwise direction viewing Figures 1 and 3, the front blade cuts into and effectually directs the air into the space between the companion blades of a pair with both blades screwing through the air to develop a maximum pull, while the rear blade effects the proper displacement of the air rearwardly to provide a maximum lifting effort.

As seen in Figure 1, each blade of a pair is substantially s-shaped in plan, including an inner, radial attaching shank I9 projecting outwardly from the hub Ill and merging into a laterally offset wider or broad section which forms the main body and air-gripping portion of the propeller. This wider section of each blade extends generally backwardly and obliquely to the radial and converges in an outward direction, terminating in a reversely-bent or curved tip portion whose free end is located substantially in the radial plane of the attaching shank l9. By thus shaping the blades, in combination with the dual blade construction, the pooheting and compressing of the air as well as its displacement is effectually regulated and controlled to provide for maximum pulling and lifting power. Furthermore, any tendency to slip or skid is effectually resisted and reduced to a minimum.

ginal side of the leading portion of said front blade being convexly curved toward the oppos-r ing face of the rear blade and the front marginal side of the trailing portion of said rear blade being convexly curved toward the opposing face of the front blade.

2. An airplane propeller, comprising a hub, and a plurality of pairs of blades radiating from said hub, the blades of each pair being disposed side by side axially of the hub to provide a comparatively narrow air pocket therebetween, each blade including a shank portion, and a comparatively broad body portion merging into a reversely curved tip portion in the plane of such body portion.

3. An airplane propeller, comprising a hub having a plurality of pairs of blades radiating therefrom, each blade including a shank portion and a comparatively broad body portion merging into a reversely curved tip portion, said body portion being laterally offset from said shank in the direction of rotation of the propeller.

MICHAEL LEFF. 

